Photosynthesis in Higher Plants Test - 23

Certain red and blue wavelengths of light are the most effective in photosynthesis, because they have exactly the right amount of energy to energize or excite, electrons in chlorophyll and boost them out of their orbits to a higher energy level in the process of photosynthesis.

Earth surface re-emits heat, obtained from the sun, in the form of infrared radiation but part of this does not escape into space as atmospheric gases (e.g., carbon dioxide, methane, etc.) absorb a major fraction of it. The molecules of these gases radiate heat energy,and a major part of which again comes to Earths surface, thus heating it up once again.This cycle is repeated many times. The gases carbon dioxide, methane, chlorofluorocarbons and nitrous oxide  are commonly known as greenhouse gases because they are responsible for the greenhouse effect. The greenhouse effect leads to global warming. Carbon dioxide is also one of the substrates used in the photosynthesis process. An increase in carbon dioxide concentration will increase the rate of photosynthesis. An increase in deserts is called desertification. Desertification will lead to the spread of desert plants. Several factors like a decrease in rainfall, atmospheric pollution, deforestation etc are responsible for the spread of deserts but desertification is not directly linked to increasing carbon dioxide concentration.

Photosynthesis traps solar energy for synthesis of organic compounds. During photosynthesis, water splits in the process called as photolysis of water. It releases oxygen as a by-product of photosynthesis.

Nutrient cycles circulate matter through the biosphere. The nutrients regularly alternate between living (biotic) and nonliving (abiotic) components. Hence, the nutrient cycles are also called as biogeochemical cycles. The important nutrient cycles are water cycle, carbon cycle, nitrogen cycle, mineral cycle. The processes that are a part of the water cycle are transpiration, evaporation, precipitation, run-off surface water, percolation of water to ground water table. The process of photosynthesis is carried out by autotrophs and traps solar energy in an ecosystem. It is not a part of the water cycle.

• According to the chemiosmosis theory of ATP generation. The ATP is generated utilizing the electrochemical gradient generated due to the accumulation of protons in the thylakoid lumen of the chloroplast. 
• The accumulation of protons gives rise to an electric gradient, due to the accumulation of positive charge and a chemical gradient due to the accumulation of hydrogen atoms. 
• When protons move along this electrochemical gradient through the  F$$_0$$ - F$$_1$$ ATP synthase enzyme complex, ATP generation occurs.

Chemosynthesis is the biological conversion of one or more carbon molecules (usually carbon dioxide or methane) and nutrients into organic matter by the use of energy from the chemical reaction between the inorganic molecules (e.g. hydrogen gas,hydrogen sulfide) or methane, rather than sunlight, as in photosynthesis e.g., Nitrobacter and sulphur bacteria.

Both mitochondria and chloroplasts are double membrane bound organelles. However, chloroplasts are absent in animal cells, unlike that of the mitochondria which are omnipresent in plant and animal cells.
Chloroplasts contain the photosynthetic pigment "chlorophyll" that traps sun's energy for the production of carbohydrate (food). Mitochondria are sites for aerobic cellular respiration and are responsible for energy generation for the proper functioning of the cells.
So, the correct answer is option A.

• Photosynthesis is a physicochemical process by which photosynthetic organisms (plants, algae, and some bacteria) use light energy from the sun to produce carbohydrate which is stored as a source of energy.
  In this process, carbon dioxide and water are taken up from the environment and oxygen is released. 
• In this process, carbon dioxide and water are taken up from the environment and oxygen is released. This occurs through a series of energy transducing reactions in the chloroplast containing the photosynthetic pigment called chlorophyll.

So, the correct answer is 'Oxidation of carbon to carbon dioxide'

Correct Answer: B

• Photorespiration is the process that occurs in $$C_3$$ plants. In this process, peroxisomes, chloroplast, and mitochondria take part. The oxygen-consuming reactions occur in peroxisomes and stroma of chloroplast while $$CO_2$$ releasing reaction occurs in mitochondria.